1. Field of the Invention
The present invention relates to an image processing method and apparatus.
2. Background Art
A typical imaging system accumulates, for example, images for one frame period and outputs the images as a one-frame picture. Thus, imaging blurring arises about a moving object.
That is, in an image, an edge of an object shows discontinuity in gradation. Assume that the object moves within the image. Even when the edge position moves, a distinct and clear image can be displayed if the edge is recorded and displayed as clear discontinuity in gradation.
In a typical imaging system, however, the motion of the object for one frame period is accumulated. Thus, the discontinuity in gradation expressing the edge is not recorded clearly, so there appears a gradation transition area having a fixed width in an image. This is blurring caused by imaging. Such blurring gives a sense of discomfort to an observer. Particularly, assume that an object observed as a distinct image when it stands still begins to move. In this case, as soon as the object moves, imaging blurring occurs so that a sense of distinction is lost suddenly. Thus, the sense of discomfort is great at the start of motion.
On the other hand, in a so-called hold type display such as a liquid crystal display (LCD), one and the same image is held and displayed for one frame period. Also in such a display, blurring of a moving object in an image is recognized by an observer due to the hold effect of eyes. Particularly, in the case of an LCD, blurring of the moving object occurs also due to its insufficient speed of response.
Therefore, in the related art, edge enhancement processing is performed to increase the sense of distinction (sharpness) of an image to be displayed when the image is displayed on a display such as a cathode ray tube (CRT) or an LCD.
As the method of edge enhancement processing, there are a method in which an edge of an input image is detected and a predetermined value is added to a video signal of the detected edge portion; a method in which the difference in gradation level between a pixel subject to edge enhancement processing and each pixel around the pixel is enhanced; and so on.
Further, as the method for applying different edge enhancement processing to still picture areas and motion picture areas, there is a method disclosed in Japanese Patent Laid-Open No. 185145/1996. According to this method, processing in which edge enhancement is not performed on any motion picture area is adopted to make the motion look smooth in the motion picture area.
However, when a motion picture with imaging blurring is displayed, the reduction of sharpness (blurring of edges) in the case where an object is moving is recognized conspicuously in comparison with the sharpness of the object in the case where the object stands still. This is due to the following reasons: When the object stands still, increase in the sharpness is attained by edge enhancement. On the other hand, when the object is moving, there occurs together the reduction of sharpness due to imaging blurring and the reduction of sharpness due to the fact that edge enhancement processing is not performed satisfactorily due to the reduction of sharpness caused by imaging blurring.
That is, in the related art, adequate researches have not been made as to how to perform edge enhancement processing to display a more natural picture image.